Amide Functionalizing tfz Topological Co 6 (μ 3 -OH) 6 -MOF for One-Step MTO Products Separation

The separation of methanol-to-olefin (MTO) products to obtain high-purity ethylene (C2H4) and propylene (C3H6) is critical. However, developing adsorbents with high adsorption capacity and selectivity for C2H4/C3H6 remains highly challenging, due to their similar physicochemical properties. Herein, a stable amide-functionalized and tfz topological metal–organic framework (MOF), [Co6(OH)6(NTB)2(NPI)3]·xguest (NJTU-Bai87, NJTU-Bai = Nanjing Tech University Bai’s group), was synthesized through mixed ligands of 4,4′,4″-nitrilotribenzoic acid (H3NTB) and N-(pyridin-4-yl)isonicotinamide (NPI), which exhibits both excellent uptake capacities of C3H6 (200.9 cm3 g–1) and C2H6 (78.2 cm3 g–1) and high selectivities for equimolar mixtures of C3H6/C2H4 (10.5) and C2H6/C2H4 (1.45) at 298 K and 1 bar, respectively. Furthermore, breakthrough experiments demonstrate that the NJTU-Bai87 could achieve one-step acquisition of polymer-grade C2H4 (≥99.9%) during C3H6/C2H4 and C2H6/C2H4 separation. Very interestingly, for C3H6/C2H4 mixture (50/50, v/v), high-purity C2H4 (≥99.9%) and C3H6 (≥99.5%) can be directly harvested or recovered upon desorption, with ultrahigh productivities of 160 and 73.8 L kg–1, respectively, which surpass many well-developed MOFs for C3H6/C2H4 separation. This work may provide valuable insights for the rational design of high-performance MOFs for practical C2H4 purification.